[GitHub] [incubator-wayang] github-actions[bot] opened a new issue, #285: create a map with specific dataset type

["github-actions[bot] (via GitHub)" <gi...@apache.org>]

github-actions[bot] opened a new issue, #285:
URL: https://github.com/apache/incubator-wayang/issues/285

   create a map with specific dataset type
   
   https://github.com/apache/incubator-wayang/blob/d46f3c3f0fb963c2ee2640f00a106042fba55431/wayang-api/wayang-api-sql/src/main/java/org/apache/wayang/api/sql/calcite/converter/WayangProjectVisitor.java#L54
   
   ```java
   
   /*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
    * with the License.  You may obtain a copy of the License at
    *
    *     http://www.apache.org/licenses/LICENSE-2.0
    *
    * Unless required by applicable law or agreed to in writing, software
    * distributed under the License is distributed on an "AS IS" BASIS,
    * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    * See the License for the specific language governing permissions and
    * limitations under the License.
    *
    */
   
   package org.apache.wayang.api.sql.calcite.converter;
   
   import org.apache.calcite.rel.core.Project;
   import org.apache.calcite.rel.type.RelDataType;
   import org.apache.calcite.rel.type.RelDataTypeField;
   import org.apache.calcite.rex.RexInputRef;
   import org.apache.calcite.rex.RexNode;
   import org.apache.wayang.api.sql.calcite.rel.WayangProject;
   import org.apache.wayang.basic.data.Record;
   import org.apache.wayang.basic.operators.MapOperator;
   import org.apache.wayang.core.function.FunctionDescriptor;
   import org.apache.wayang.core.plan.wayangplan.Operator;
   
   import java.util.ArrayList;
   import java.util.List;
   
   public class WayangProjectVisitor extends WayangRelNodeVisitor<WayangProject> {
       WayangProjectVisitor(WayangRelConverter wayangRelConverter) {
           super(wayangRelConverter);
       }
   
       @Override
       Operator visit(WayangProject wayangRelNode) {
   
           Operator childOp = wayangRelConverter.convert(wayangRelNode.getInput(0));
   
           /* Quick check */
           List<RexNode> projects = ((Project) wayangRelNode).getProjects();
           for(RexNode rexNode : projects) {
               if (!(rexNode instanceof RexInputRef)) {
                   throw new IllegalStateException("Generalized Projections not supported yet");
               }
           }
   
           //TODO: create a map with specific dataset type
           MapOperator<Record, Record> projection = new MapOperator(
                   new MapFunctionImpl(projects),
                   Record.class,
                   Record.class);
   
           childOp.connectTo(0, projection, 0);
   
           return projection;
       }
   
   
       private class MapFunctionImpl implements
               FunctionDescriptor.SerializableFunction<Record, Record> {
   
           private final int[] fields;
   
           private MapFunctionImpl(int[] fields) {
               this. fields = fields;
           }
   
           private MapFunctionImpl(List<RexNode> projects) {
               this(getProjectFields(projects));
           }
   
           @Override
           public Record apply(Record record) {
   
               List<Object> projectedRecord = new ArrayList<>();
               for(int field : fields) {
                   projectedRecord.add(record.getField(field));
               }
   
               return new Record(projectedRecord.toArray(new Object[0]));
           }
       }
   
       private static int[] getProjectFields(List<RexNode> projects) {
           final int[] fields = new int[projects.size()];
           for (int i = 0; i < projects.size(); i++) {
               final RexNode exp = projects.get(i);
               if (exp instanceof RexInputRef) {
                   fields[i] = ((RexInputRef) exp).getIndex();
               } else {
                   return null; // not a simple projection
               }
           }
           return fields;
       }
   }
   
   ```
   
   17020a1705b3f23ce8e4515424eb3397d5f2876c


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